Hello aspirant.
Friatly it depends on the college or university you are applying for.
Mumbai university takes top 5 sub scores, English compulsory.
Delhi University takes top 4 sub scores, English compulsory.
The CBSC board has a best of five rule in which your main percentage is decided by one language subject Ie English and other 4 subjects.
Yes u should consider top 5 subjects for calculating your aggregate percentage
It entirely depends on the Institute in which you would like to study. For exam in university of Delhi you are supposed to calculate your percentage best of three either PCM combination works or PCB where English is required.
I feel languages gives you percentage which makes your percentage better with top 20
PCMB makes you percentage better with the subject your choosing for options or language.i would prefer you to choose the language which you know better and get high score. All the best. Thank you.